Laser direct overall water splitting for H₂ and H₂O₂ production.

Abstract

Hydrogen (H₂) and hydrogen peroxide (H₂O₂) play crucial roles as energy carriers and raw materials for industrial production. However, the current techniques for H₂ and H₂O₂ production rely on complex catalysts and involve multiple intermediate steps. In this study, we present a straightforward, environmentally friendly, and highly efficient laser-induced conversion method for overall water splitting to simultaneously generate H₂ and H₂O₂ at ambient conditions without any catalysts. The laser direct overall water splitting approach achieves an impressive light-to-hydrogen energy conversion efficiency of 2.1%, with H₂ production rates of 2.2 mmol/h and H₂O₂ production rates of 65 µM/h in a limited reaction area (1 mm²) within a short real reaction time (0.36 ms/h). Furthermore, we elucidate the underlying physics and chemistry behind the laser-induced water splitting to produce H₂ and H₂O₂. The laser-induced cavitation bubbles create an optimal microenvironment for water-splitting reactions because of the transient high temperatures (10⁴ K) surpassing the chemical barrier required. Additionally, their rapid cooling rate (10¹⁰ K/s) hinders reverse reactions and facilitates H₂O₂ retention. Finally, upon bubble collapse, H₂ is released while H₂O₂ remains dissolved in the water. Moreover, a preliminary amplification experiment demonstrates the potential industrial applications of this laser chemistry. These findings highlight that laser-based production of H₂ and H₂O₂ from water holds promise as a straightforward, environmentally friendly, and efficient approach on an industrial scale beyond conventional chemical catalysis.